This invention relates to an improved treatment of hides and skins including green or dehydrated skins and hides, which for convenience will be called xe2x80x98skins and hidesxe2x80x99 throughout the specification.
Skins and hides have been treated to produce leather for centuries, and a typical tanning process generally includes the curing of the green skin or hide by salting or drying prior to shipping to the tannery. At the tannery the cured skins are soaked in water to remove the salt and also any blood and dirt. This soaking may take from hours to seven days depending on the condition of the skins. The flesh is then removed from the inner surface and to loosen the hair the skin is immersed in a solution of lime and sodium sulphide from one up to nine days following which the hair is removed by a dehairing machine.
Also it is often necessary to pass the skin or hide through a dry cleaning solution to remove the fats and proteins from the skin or hide.
The skins or hides are then soaked in a weak solution of acid and simultaneously most skins are subject to a bating process. Following this the skins or hides are tanned, either by vegetable tanning which may take several weeks or months, or by chrome tanning which may be completed in a single day, the tanning involving the immersion of the skins or hides in two different liquors in a tumbling drum.
The leathers can then be lubricated and dyed, with final drying on stretching frames.
In our previous application PCT/AU97/00262 there is described a process and apparatus for the treatment of skins or hides which includes the selection of a skin or hide, stretching the skin or hide by toggles on a frame to a desired configuration and applying a chamber to the upper side of the skin or hide, sealing the chamber to the skin or hide and applying a pressurised liquor in the chamber so that the liquor penetrates the skin or hide. Means are provided on the undersurface of the skin or hide to support the distended skin or hide and also to sense the presence of the liquor penetrating the skin or hide to provide control of the treatment of the skin or hide.
However the treatment liquor must be applied to the inside of the skin or hide, that is the side opposite to the outer or wool or hair side of the skin or hide. Thus in the above specification the liquor is applied to the upper side of the skin or hide and the lower side of the skin or hide has the wool or hair attached thereto.
In tanning operations it is necessary for the wool or hair to be removed from the skin or hide, and in the above described process this can only be done when the skin or hide is removed from the toggles and the hair or wool removed before the next tanning process and the skin again attached to the toggles to maintain the stretched condition during the subsequent tanning or other treatment processes by being passed from treatment station to the next.
It is an object of the invention to provide a skin or hide treatment process or tanning process in which the process can be achieved at one station.
It is another object of the invention to provide a process and apparatus whereby the wool or hair can be easily removed without removal of the skin or hide from the apparatus.
It is a still further object of the invention to provide a process for the treatment of skins or hides whereby the process can be controlled with precision.
Another object of the invention of the invention is to provide a method and apparatus wherein the time required for treatment and tanning of the skin or hide is considerably reduced.
A still further object of the invention is to provide a method and apparatus wherein the skin or hide is treated in a stretched condition, the skin or hide remaining in the stretched condition after treatment.
Another object of the invention is to stretch the skin or hide by pressurised liquor so that fibres and cells of the skin or hide are opened to whereby the treatment liquor readily penetrates the skin or hide.
A further object of the invention is to provide a process and apparatus for the treatment of skins or hides in which the treatment liquors are recycled and/or processed to collect the materials removed from the skin or hide by the processing liquor.
A still further object of the invention is to a process and apparatus in which the pressure applied to the liquid not only accelerates the entry of the liquor into the skin or hide, but also provides the means of stretching the skin or hide to open the fibre structure.
Thus there is provided according to the invention a process for the treatment of skins or hides, the process including the steps of positioning the skin or hide on a frame, with the flesh side adjacent the frame, sealing the edges of the skin or hide to the support, applying treatment liquor under pressure between the skin or hide and support whereby the skin or hide is distended and stretched by the liquor under pressure to open the structure of the skin or hide to permit penetration of the treatment liquor into the skin or hide.